1. Field of the Invention
The present invention relates to a capsule medical apparatus such as a capsule endoscope for traveling in a lumen with a liquid such as water, which is introduced into a subject, to observe inside the lumen and a body-cavity observation method.
2. Description of the Related Art
Recently, in a field of endoscopes, a capsule endoscope having an imaging function and a radio communication function has been appearing. This capsule endoscope includes a structure for displacing along with peristaltic movement in an internal organ (in a lumen) such as the esophagus, stomach and small intestine and sequentially taking images with its imaging function until it is naturally discharged from the body of the subject, after swallowed by the subject through his or her mouth for the observation (examination).
WO 02/95351 discloses a technique suited for observing the large intestine, in which the specific gravity of the capsule endoscope is set as same as that of the liquid therearound or 1 which is same as that of water so that, when a subject swallows the capsule endoscope with the liquid, the capsule endoscope floats in the liquid and travels quickly in the body-cavity to the large intestine. When the capsule endoscope is attached to the wall surface of the body-cavity, only close narrow area is imaged; however, according to WO 02/95351, since the capsule endoscope floats in the liquid to observe, an observing field is maintained and every part can be observed.
Regarding observations of inside hollow organs such as the large intestine with the use of such a capsule endoscope, an entire of the lumen may be needed to be observed in some cases and a particular portion such as a polyp (lumen wall) may be needed to be observed in other cases. In order to meet such demands, for example, WO 03/11103 discloses a capsule endoscope having at least one illumination source, at least one imaging sensor, and at least two optic systems. Further, WO 02/54932 discloses a capsule endoscope having at least one imaging device and an optic system including a plurality of optical paths. According to WO 03/11103 and WO 02/54932, the capsule endoscope is capable of imaging the lumen not only in the axial direction of the lumen but also in an inner wall direction of the lumen in the hollow organ.
However, according to the capsule endoscope of WO 03/11103 and WO 02/54932, the system depends on the structure of the imaging optical system in the capsule endoscope and in order to optimize imaging direction to perform a proper observation in the lumen in its axial direction and the inner wall direction, more optic systems or optical paths are required to be set. Thus, the structure becomes more complex and enlarged so that the proper size of the capsule endoscope to be introduced into a subject cannot be maintained.